Method of precooking paste in dry cells



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Iran. sATn LAUCHL IN OURRIE, OF LAKEWOOD, OHIO, ASSIGNOR TO NATIONAL CARBON COM- PANY, INC., A CORPORATION OF NEW YORK METHOD OF PRECOOKING PASTEIN DRY CELLS This invention relates to dry cells and has particular reference to improvements in the method of forming a paste layer on the inside surface of the zinc electrodes of such cells. The invention is especially applicable to the manufacture of dry cells of the bobbin type in which the depolarizingmixture is formed about a centrally located carbon electrode and then inserted into a paste lined zinc container.

In Patents Numbers 1,295,475 and 1,375,- 202 both granted to French and Benner, methods are described in which a paste layer is applied to substantially the entire inner surface of the zinc cups and is gelatinized thereon by suitable application of heat.

The present invention is an improved method of preco'oking the paste layer on the inner surfaces of zinc electrodes in such a manner as to produce a uniform tough and tenacious coating with a'minimum of mechanical operation. With the zinc cups so lined a very good contact is obtained between the zinc and the paste and the necessity for fabric wrappingof the bobbin may be eliminated. lhese facts tend to improve the service characteristics of the cell as well as the economy of manufacture.

, According to my invention paste is placed in a zinc cup electrode and a plunger, preferably of substantially the same diameter as the regular mix bobbin and composed of hard rubber, wood, or other inert material, is then inserted into the cup or can. As the inert plunger is forced to the bottom of the can, the paste is forced upward around the plunger filling the space between the plunger and the zinc can and completely covering the in.- ner surface of said can to the desired height: The can, with the plunger thus in position, is placed in a hot water bath-and the paste cooked until a uniform layer of the desired thickness is deposited on the inner surface of the can. Upon withdrawal of the plunger the uncooked pasteis allowed to flow again Application filed August 29, 1927. Serial No. 216,329.

to the bottom of the can. The regular bobbin of depolarizer mix is then inserted into the can as in standard practice, the uncooked paste being forced up into the space between the bobbin and the cooked paste layer thus forming a good contact between the two. The cell may be completed in the usual-manner by placing sawdust, paper, or the like, over the bobbin, and applying a plastic sealingrnaterial.

The amount of paste originally added to the zinc can may vary depending on the size of cell to be made and the thickness of the paste coating desired. ll may use approxipaste forced upward by the plunger does not reach the top of the zinc cup. A clean annular area is maintained about the top of the cup, this clean surface being desirable to insure proper, sealing of the completed cell.

An ordinary flour and water paste has been found to be satisfactory although other paste compositions which will harden sufiiciently upon heating to the temperature of boiling water may be used. With the preferred paste from 5 to 15 seconds immersion in a water bath at a temperature of approximately 100 C. is sufiicient to cook the paste.

While reference has been made to the use of this invention in the making of flashlight type cells, it is also applicable to cells of larger sizes and in fact to any type of cell requiring a paste lining adjacent to the inner surface of a hollow electrode. The necessity of an additional lining between the depolarizing mix and the zinc can when using this precooked paste lining is somewhat dependent on the size of the-cell.

As applied to the larger or commonly called 6-inch cell I prefer an original addition of approximately 60 grams of paste to the zinc can. lVith the plunger inserted and centered t e can is placed in a water bath at a temperature of about 100 C. for 6 to 8 seconds. The plunger and uncooked paste is then removed, the can edges cleaned if necessary, and the can placed in a drying oven at 100 C. for 6 to 8 minutes to further toughen the paste coating. The cell isthen completed in any usual, manner as by inserting a paste coated pulp-board liner and tamping the desired mix into the annular space between this liner and the carbon rod electrode.

I claim:

1. A method of forming a paste lining on a dry cell zinc electrode which consists in placing a predetermined amount of raw paste within said electrode and distributing said raw paste uniformly thereon by insertion of a bobbin shaped plunger of inert material into said electrode, and applying heat to cook the paste.

- 2.-A method of forming a paste lining on the inner surface of a dry cell container which comprises adding raw paste to the bottom of the container, distributing said paste uniformly by insertion of a bobbin shaped plunger of inert mateiral into said container, and applying heat to cook the paste.

3. A method of forming a paste lining on a dry cell can which consists in adding paste to the bottom of the can, inserting a bobbin shaped plunger of inert material into the can to force the paste upward and around said plunger so that the inner surface of said can is uniformly covered with paste, and applying heat to cook the paste.

4. A method of forming a paste lining on I the inner surface of a dry cell can which consists in adding paste to the bottom of the can, inserting a bobbin shaped plunger of inertmaterial into the can to force the paste into the space between the plunger and the inner surface of the can, and heating in hot water to cook a part of the paste.

5. A method of forming a layer of cooked paste on the inner surface of a zinc dry cell container before insertion of the depolarizing mixture which consists in placing the required amount of paste in the container and distributing the raw paste by means of an inert bobbin shaped plunger, and heating in a hotwater bath to cook the paste.

6. The steps in the process of assembling a dry cell which consist'in placing paste in the bottom of a 'zinc can, inserting a bobbin shaped plunger of inert material to distribute the paste uniformly over the inner surface of said can, applying heat to cook part of the paste, removing plunger and allo uncooked paste to flow to the bottom of the can,

inserting bobbin of depolarizingmix and ing the paste-level; and heating the paste to render it non-fluid.

In testimony whereof, I aflix my signature.

LAUCHLIN M. CURRIE. 

